Conventional computing systems may include a discrete graphics processing unit (dGPU) or an integral graphics processing unit (iGPU). The discrete GPU and integral GPU are heterogeneous because of their different designs. The integrated GPU generally has relatively poor processing performance compared to the discrete GPU. However, the integrated GPU generally consumes less power compared to the discrete GPU.
The conventional operating system does not readily support co-processing using such heterogeneous GPUs. Referring to FIG. 1, a graphics processing technique according to the conventional art is shown. When an application 110 starts, it calls the user mode level runtime application programming interface (e.g., DirectX API d3d9.dll) 120 to determine what display adapters are available. In response, the runtime API 120 enumerates the adapters that are attached to the desktop (e.g., the primary display 180). A display adapter 165, 175, even recognized and initialized by the operating system, will not be enumerated in the adapter list by the runtime API 120 if it is not attached to the desktop. The runtime API 120 loads the device driver interface (DDI) (e.g., user mode driver (umd.dll)) 130 for the GPU 170 attached to the primary display 180. The runtime API 120 of the operating system will not load the DDT of the discrete GPU 175 because the discrete GPU 175 is not attached to the display adapter. The DDI 130 configures command buffers of the graphics processor 170 attached to the primary display 180. The DDI 130 will then call back to the runtime API 120 when the command buffers have been configured.
Thereafter, the application 110 makes graphics requests to the user mode level runtime API (e.g., DirectX API d3d9.dll) 120 of the operating system. The runtime 120 sends graphics requests to the DDI 130 which configures command buffers. The DDI calls to the operating system kernel mode driver (e.g., DirectX driver dxgkrnl.sys) 150, through the runtime API 120, to schedule the graphics request. The operating system kernel mode driver then calls to the device specific kernel mode driver (e.g., kmd.sys) 150 to set the command register of the GPU 170 attached to the primary display 180 to execute the graphics requests from the command buffers. The device specific kernel mode driver 160 controls the GPU 170 (e.g., integral GPU) attached to the primary display 180.
In U.S. patent application Ser. No. 12/649,317 filed Dec. 29, 2009, and U.S. patent application Ser. No. 12/651,395 filed Dec. 21, 2009 various techniques for using the discrete GPU to process graphics data and commands are disclosed. When using the discrete GPU, graphics data and commands are transferred across one or more communication links such as peripheral component interface express buss. The transfer of graphics data and commands, however, may result in a bandwidth bottleneck on the communication link. Accordingly, there is a continuing need for improved techniques for transferring graphics data and commands across a communication link to the discrete graphics processing unit.